Quick Summary
- Colorless, volatile liquid with pleasant fruity smell
- Boiling point: 77°C, Melting point: -84°C
- Slightly soluble in water, highly soluble in organic solvents
- Less dense than water (density: 0.902 g/cm³)
- Highly flammable with sweet-smelling vapor
What is Ethyl Ethanoate?
Ethyl ethanoate is an ester formed when ethanoic acid (acetic acid) reacts with ethanol. It belongs to the ester family of organic compounds. You can recognize esters by their pleasant smells – they give fruits their characteristic scents.
The chemical formula is C₄H₈O₂ or CH₃COOC₂H₅. In Nigeria, you might find ethyl ethanoate in nail polish remover, glue, and some cleaning products. Its sweet smell makes it easy to identify in the chemistry lab.
Detailed Physical Properties
1. Appearance and Color
Ethyl ethanoate is a clear, colorless liquid at room temperature. When you pour it into a test tube, it looks like water. However, unlike water, it has a distinct fruity smell that reminds people of pears or apples.
The liquid is transparent, meaning light passes through it easily. This property makes it useful in industries where clear solutions are needed, such as perfume making.
2. Odor (Smell)
The most noticeable property of ethyl ethanoate is its pleasant, sweet smell. Students often describe it as fruity or like nail polish remover. This characteristic smell comes from the ester functional group (-COO-).
In WAEC practical exams, you might be asked to identify an unknown liquid. If it smells sweet and fruity, think of esters like ethyl ethanoate. However, never smell chemicals directly – always waft the vapor toward your nose using your hand.
3. Boiling Point and Melting Point
Ethyl ethanoate has a relatively low boiling point of 77°C (some sources say 75-77°C). This is much lower than water’s boiling point (100°C). The low boiling point tells us that ethyl ethanoate molecules have weak forces between them.
The melting point is -84°C, which means it freezes at very low temperatures. In Nigeria’s warm climate, you will never see frozen ethyl ethanoate – it remains liquid year-round.
Why is the boiling point low? Esters have polar molecules, but they cannot form hydrogen bonds like alcohols or carboxylic acids. Only weak dipole-dipole forces and van der Waals forces hold the molecules together, so less heat is needed to separate them.
4. Volatility
Ethyl ethanoate is highly volatile, meaning it evaporates quickly at room temperature. If you spill some on your desk, it will disappear within minutes as it turns into vapor.
This volatility makes it useful as a solvent in industries. For example, when you paint your nails with nail polish, the ethyl ethanoate solvent evaporates quickly, leaving the colored coating behind.
5. Solubility
Ethyl ethanoate shows limited solubility in water (about 8g dissolves in 100ml of water at 20°C). This is because ethyl ethanoate is slightly polar, but not polar enough to mix completely with highly polar water molecules.
However, it dissolves very well in organic solvents like benzene, ethanol, and acetone. The rule “like dissolves like” applies here – ethyl ethanoate (organic) dissolves in other organic substances.
In the lab, if you need to dissolve a non-polar or slightly polar substance, ethyl ethanoate works better than water. This property makes it valuable for extracting organic compounds from mixtures.
6. Density
The density of ethyl ethanoate is 0.902 g/cm³ at 20°C. This is less than water’s density (1.0 g/cm³), so ethyl ethanoate floats on water. If you pour ethyl ethanoate into a beaker of water, it will form a layer on top.
This density difference is useful for liquid-liquid extraction in the lab. You can separate ethyl ethanoate from aqueous solutions using a separating funnel.
7. Flammability
Ethyl ethanoate is highly flammable. It catches fire easily and burns with a clean flame. The flash point (lowest temperature at which it can ignite) is -4°C, which is very low.
Safety tip: Always keep ethyl ethanoate away from open flames, sparks, or hot surfaces in the laboratory. Store it in cool, well-ventilated areas. If you use it in a practical exam, make sure no Bunsen burners are nearby.
8. Vapor Pressure
Ethyl ethanoate has high vapor pressure at room temperature (about 97 mmHg at 25°C). High vapor pressure means many molecules escape from the liquid surface into the air. This explains why the sweet smell spreads quickly when you open a bottle of nail polish remover.
Comparison Table: Ethyl Ethanoate vs Similar Compounds
| Property | Ethyl Ethanoate | Ethanol | Ethanoic Acid |
|---|---|---|---|
| Formula | CH₃COOC₂H₅ | C₂H₅OH | CH₃COOH |
| Smell | Sweet, fruity | Alcoholic | Sour, vinegar-like |
| Boiling Point | 77°C | 78°C | 118°C |
| Density | 0.902 g/cm³ | 0.789 g/cm³ | 1.049 g/cm³ |
| Solubility in Water | Slightly soluble (8g/100ml) | Completely soluble | Completely soluble |
| Functional Group | Ester (-COO-) | Alcohol (-OH) | Carboxylic acid (-COOH) |
Common Exam Mistakes
Based on WAEC Chief Examiner reports, students often make these errors:
- Confusing boiling points: Students write 75°C, 77°C, or even 78°C for ethyl ethanoate. The accepted value is 77°C (though 75-77°C range is acceptable). Don’t confuse it with ethanol’s boiling point (78°C).
- Wrong solubility description: Many students say “insoluble in water” which is incorrect. Ethyl ethanoate is slightly soluble in water, not completely insoluble. Know the difference: insoluble (0-0.1g/100ml), slightly soluble (0.1-10g/100ml), soluble (>10g/100ml).
- Vague smell description: Writing “it has a smell” earns no marks. Be specific: “pleasant fruity smell” or “sweet smell like nail polish remover.”
- Missing safety information: When asked about physical properties, students forget to mention flammability. Always include safety-related properties when discussing volatile organic compounds.
- Confusing physical and chemical properties: Students sometimes mention “it undergoes hydrolysis” under physical properties. Remember: physical properties don’t change the substance’s chemical identity. Hydrolysis is a chemical property.
Practice Questions
Multiple Choice Questions
1. What is the boiling point of ethyl ethanoate?
a) 78°C
b) 77°C ✓
c) 100°C
d) 118°C
2. Which of the following best describes the solubility of ethyl ethanoate in water?
a) Completely soluble
b) Insoluble
c) Slightly soluble ✓
d) Forms a colloidal solution
3. The characteristic smell of ethyl ethanoate can be described as:
a) Sour like vinegar
b) Pungent like ammonia
c) Pleasant and fruity ✓
d) Rotten eggs
4. If ethyl ethanoate is poured into water, it will:
a) Sink to the bottom
b) Float on top ✓
c) Mix completely
d) Form a precipitate
5. Why does ethyl ethanoate evaporate quickly at room temperature?
a) It has strong hydrogen bonding
b) It has high vapor pressure ✓
c) It is denser than air
d) It reacts with air
Essay Questions
1. (a) State FOUR physical properties of ethyl ethanoate. (4 marks)
(b) Explain why ethyl ethanoate has a lower boiling point than ethanoic acid. (3 marks)
Marking guide:
(a) Award 1 mark each for: colorless liquid, fruity smell, boiling point 77°C, slightly soluble in water, volatile, density 0.902 g/cm³, flammable (any 4)
(b) Award marks for mentioning: ethanoic acid forms hydrogen bonds (1 mark), ethyl ethanoate cannot form hydrogen bonds (1 mark), stronger intermolecular forces require more heat to overcome (1 mark)
2. A student was given three colorless liquids labeled X, Y, and Z. Liquid X has a fruity smell and floats on water. Liquid Y smells like vinegar and mixes completely with water. Liquid Z has an alcoholic smell and also mixes with water.
(a) Identify liquids X, Y, and Z. (3 marks)
(b) Suggest ONE way to distinguish between liquids Y and Z. (2 marks)
Marking guide:
(a) X = ethyl ethanoate (1 mark), Y = ethanoic acid (1 mark), Z = ethanol (1 mark)
(b) Test with sodium carbonate/sodium hydrogencarbonate – Y (acid) will produce CO₂ bubbles, Z (alcohol) will not react (2 marks). Or use litmus paper – Y turns blue litmus red (1 mark), Z does not affect litmus (1 mark)
3. Explain why ethyl ethanoate is a good solvent for organic substances but not for ionic compounds. (5 marks)
Marking guide:
Award marks for: ethyl ethanoate is a non-polar/slightly polar organic solvent (1 mark), organic substances are also non-polar/slightly polar (1 mark), “like dissolves like” principle (1 mark), ionic compounds are highly polar/charged (1 mark), ethyl ethanoate cannot break ionic bonds or effectively solvate ions (1 mark)
Memory Aids
Acronym: “CFBSVD”
Remember the main physical properties of ethyl ethanoate:
- Colorless liquid
- Fruity smell
- Boils at 77°C
- Slightly soluble in water
- Volatile (evaporates quickly)
- Density less than water (0.902)
Association Trick
“Nail Polish = Not Polar” – Remember that ethyl ethanoate (found in nail polish remover) is NOT very polar, which explains why it doesn’t dissolve well in water but dissolves organic substances.
Boiling Point Sequence
Remember the order: Ethyl ethanoate (77) < Ethanol (78) < Water (100) < Ethanoic acid (118)
The numbers increase with hydrogen bonding strength.